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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Ocean Engineering and Technology
Journal Basic Information
Journal DOI :
Korean Society of Ocean Engineers
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Volume & Issues
Volume 26, Issue 6 - Dec 2012
Volume 26, Issue 5 - Oct 2012
Volume 26, Issue 4 - Aug 2012
Volume 26, Issue 3 - Jun 2012
Volume 26, Issue 2 - Apr 2012
Volume 26, Issue 1 - Feb 2012
Selecting the target year
Global Path Planning for Autonomous Underwater Vehicles in Current Field with Obstacles
Lee, Ki-Young ; Kim, Su-Bum ; Song, Chan-Hee ;
Journal of Ocean Engineering and Technology, volume 26, issue 4, 2012, Pages 1~7
DOI : 10.5574/KSOE.2012.26.4.001
This paper deals with the global path planning problem for AUVs (autonomous underwater vehicles) in a tidal current field. The previous researches in the field were unsuccessful at simultaneously addressing the two issues of obstacle avoidance and tidal current-based optimization. The use of a genetic algorithm is proposed in this paper to move past this limitation and solve both issues at once. Simulation results showed that the genetic algorithm could be applied to generate an optimal path in the field of a tidal current with multiple obstacles.
Nesting Expert System using Heuristic Search
Sheen, Dong-Mok ;
Journal of Ocean Engineering and Technology, volume 26, issue 4, 2012, Pages 8~14
DOI : 10.5574/KSOE.2012.26.4.008
Two dimensional nesting is a common problem in industries such as the shipbuilding, automotive, clothing, shoe-making, and furniture industries, in which various parts are cut off from stock or packed in a flat space while minimizing waste or unoccupied space. Nesting is known as an NP-complete problem, which has a solution time proportional to the superpolynomial of the input size. It becomes practically impossible to find an optimal solution using algorithmic methods as the number of shapes to nest increases. Therefore, heuristic methods are commonly used to solve nesting problems. This paper presents an expert system that uses a heuristic search method based on an evaluation function for nesting problems, in which parts and stock are represented by pixels. The system is developed in CLIPS, an expert system shell, and is applied to four different kinds of example problems to verify its applicability in practical problems.
Design of Bow Shape to Decrease Green Water Impact Loading in Regular Waves
Ha, Yoon-Jin ; Lee, Young-Gill ; Jeong, Kwang-Leol ;
Journal of Ocean Engineering and Technology, volume 26, issue 4, 2012, Pages 15~22
DOI : 10.5574/KSOE.2012.26.4.015
In this research, the relationship between the bow shape and green water phenomenon on the bow deck of an FPSO was studied using an experimental method. A 140,000 DWT FPSO was used as the objective hull form in the present research. The incident waves were regular types. The heights were 1.0 and 1.5 times the freeboard, and the length was equal in size to LBP. The wave heights and pressures on the deck were measured in experiments. Model tests were performed to determine the effects of bow flare angles, bow shapes, and a forecastle deck. The free heave and pitch conditions were applied to the models in these experiments. From the results of the model tests, an optimized bow shape was designed, which was found to decrease the green water impact loading. The results of this research could be used as fundamental data in the design of a bow shape.
Study on Development of GIS based Maritime Boundary Delimitation Support System
Lee, Dong-Chul ; Kim, Kye-Hyun ; Park, Yong-Gil ;
Journal of Ocean Engineering and Technology, volume 26, issue 4, 2012, Pages 23~29
DOI : 10.5574/KSOE.2012.26.4.023
Korea has maritime jurisdiction over an area 4.5 times larger than the nation`s inland area, but negotiations with surrounding nations on the maritime boundary delimitation have still not been completed satisfactorily. In particular, maritime boundary delimitation has become an important issue in terms of maritime security and resource exploration. Considering national interests, the delimitation of the maritime boundary is essential. However, no system to help the decision-makers involved in maritime boundary delimitation has yet been systematically constructed. Therefore, the aim of this study was the development of a system to support such decision-making. In this study, considerations related to maritime boundary delimitation were investigated through expert advice and international precedents. Based on these considerations, data were collected from several organizations, and a spatial database was systematically constructed. Finally, MBDSS (maritime boundary delimitation support system) was developed to support maritime boundary delimitation. This GIS-based system provides visual information about the considerations for the maritime boundary delimitation. Thus, it could help decision-makers to choose appropriate boundaries during the negotiation. Furthermore, this system is expected to be utilized as a scientific tool on the delimitation of maritime boundaries.
Underwater Radiated Noise Analysis for Commercial Ship Using Power Flow Analysis
Kwon, Hyun-Wung ; Hong, Suk-Youn ; Song, Jee-Hun ;
Journal of Ocean Engineering and Technology, volume 26, issue 4, 2012, Pages 30~36
DOI : 10.5574/KSOE.2012.26.4.030
Recently, the underwater radiated noises generated from large commercial ships have become a globally important issue. Countries with large ports and environmental protection organizations demand strict safety guidelines in relation to underwater radiated noise. In this paper, the coupled PFFE/PFBE method is used to investigate the vibration and underwater radiated noise of a commercial ship. PFFEM is employed to analyze the vibrational responses of the commercial ship, and PFBEM is applied to analyze the underwater radiation noise. The vibrational energy of the structure is treated as an acoustic intensity boundary condition of PFBEM to calculate the underwater radiation noise. Numerical simulations are presented for the commercial ship under various frequencies, and reliable results are obtained.
Design and Performance Test of Savonius Tidal Current Turbine with CWC
Jo, Chul-Hee ; Lee, Jun-Ho ; Rho, Yu-Ho ; Ko, Kwang-Oh ; Lee, Kang-Hee ;
Journal of Ocean Engineering and Technology, volume 26, issue 4, 2012, Pages 37~41
DOI : 10.5574/KSOE.2012.26.4.037
Due to global warming, the need to secure alternative resources has become more important nationally. Because of the very strong current on the west coast, with a tidal range of up to 10 m, there are many suitable sites for the application of TCP (tidal current power) in Korea. In the southwest region, a strong current is created in the narrow channels between the numerous islands. A rotor is an essential component that can convert tidal current energy into rotational energy to generate electricity. The design optimization of a rotor is very important to maximize the power production. The performance of a rotor can be determined using various parameters, including the number of blades, shape, sectional size, diameter, etc. There are many offshore jetties and piers with high current velocities. Thus, a VAT (vertical axis turbine) system, which can generate power regardless of flow direction changes, could be effectively applied to cylindrical structures. A VAT system could give an advantage to a caisson-type breakwater because it allows water to circulate well. This paper introduces a multi-layer vertical axis tidal current power system. A Savonius turbine was designed, and a performance analysis was carried out using CFD. A physical model was also demonstrated in CWC, and the results are compared with CFD.
Out-of-plane Structural Intensity Analysis of Rectangular Thick Plate
Kim, Kook-Hyun ; Cho, Dae-Seung ;
Journal of Ocean Engineering and Technology, volume 26, issue 4, 2012, Pages 42~49
DOI : 10.5574/KSOE.2012.26.4.042
A numerical method is presented for an out-of-plane structural intensity analysis of rectangular thick plates with arbitrary elastic edge constraints. The method adapts an assumed mode method based on Timoshenko beam functions to obtain the velocities and internal forces needed for a structural intensity analysis. To verify the presented method, the structural intensity of a square thick plate under harmonic force excitation, for which four edges are simply supported, is analyzed, and the result is compared with existing solutions using the assumed mode method based on trigonometric functions. In addition, numerical analyses are carried out for a rectangular-shaped thick plate under harmonic force excitations, of which three edges are simply supported and one edge utilizes an arbitrary elastic edge constraint. These numerical examples show the good accuracy and applicability of the presented method for rectangular thick plates with arbitrary edge constraints.
Effect on Vessel Motion Caused by Mitigation of Sloshing Impact Loads using Floaters
Nam, Jung-Woo ; Kim, Kyung-Sung ; Hwang, Sung-Chul ; Heo, Jae-Kyung ; Park, Jong-Chun ; Kim, Moo-Hyun ;
Journal of Ocean Engineering and Technology, volume 26, issue 4, 2012, Pages 50~56
DOI : 10.5574/KSOE.2012.26.4.050
When a liquid cargo tank is partially filled with fluid, internal impact loads can be occurred from the vessel`s motions. In this study, liquid sloshing problems with a thin top layer of particles with a lighter density than water and the coupling effects of the liquid-sloshing/vessel-motion were investigated in order to reduce the sloshing-induced impact loads. The PNU-MPS (Pusan-National-University-modified Moving Particle Simulation) method for solving the liquid motion inside a tank and the CHARM3D BEM (Boundary Element Method) based time-domain ship motion analysis program for vessel-motion simulation were coupled. From the simulation results, we could see that the floaters seemed to be quite effective at reducing the sloshing impact loads in the case of tank-only sloshing problems, but not as much for the coupling problem with vessel motion.
Classification of Transient Signals in Ocean Background Noise Using Bayesian Classifier
Kim, Ju-Ho ; Bok, Tae-Hoon ; Paeng, Dong-Guk ; Bae, Jin-Ho ; Lee, Chong-Hyun ; Kim, Seong-Il ;
Journal of Ocean Engineering and Technology, volume 26, issue 4, 2012, Pages 57~63
DOI : 10.5574/KSOE.2012.26.4.057
In this paper, a Bayesian classifier based on PCA (principle component analysis) is proposed to classify underwater transient signals using
order LPC (linear predictive coding) coefficients as feature vector. The proposed classifier is composed of two steps. The mechanical signals were separated from biological signals in the first step, and then each type of the mechanical signal was recognized in the second step. Three biological transient signals and two mechanical signals were used to conduct experiments. The classification ratios for the feature vectors of biological signals and mechanical signals were 94.75% and 97.23%, respectively, when all 16 order LPC vector were used. In order to determine the effect of underwater noise on the classification performance, underwater ambient noise was added to the test signals and the classification ratio according to SNR (signal-to-noise ratio) was compared by changing dimension of feature vector using PCA. The classification ratios of the biological and mechanical signals under ocean ambient noise at 10dB SNR, were 0.51% and 100% respectively. However, the ratios were changed to 53.07% and 83.14% when the dimension of feature vector was converted to three by applying PCA. For correct, classification, it is required SNR over 10 dB for three dimension feature vector and over 30dB SNR for seven dimension feature vector under ocean ambient noise environment.
Evaluation of Corrosion Property of Welding Zone of Stainless Steel by Laser Welding
Moon, Kyung-Man ; Won, Jong-Pil ; Park, Dong-Hyun ; Kim, Yun-Hae ; Lee, Myung-Hoon ; Kim, Jin-Gyeong ;
Journal of Ocean Engineering and Technology, volume 26, issue 4, 2012, Pages 64~69
DOI : 10.5574/KSOE.2012.26.4.064
Laser welding was carried out on austenitic 304 (STS 304) and 22 APU stainless steels. In this case, the differences between the corrosion characteristics of the welding zones of the two stainless steels were investigated using electrochemical methods. The Vickers hardness values of the weld metal (WM) zones in both cases, the STS 304 and 22 APU stainless steels, showed relatively higher values than those of other welding zones. The corrosion current densities of the heat affected zone (HAZ) of the 22 APU and the base metal (BM) zone of the STS 304 exhibited the highest values compared to the other welding zones. It is generally accepted that when STS 304 stainless steel is welded using a general welding method, intergranular corrosion is often observed at the grain boundary because of its chromium depletion area. However, when laser welding was performed on both the STS 304 and 22 APU stainless steels, no intergranular corrosion was observed at any of the welding zones. Consequently, it is considered that the intergranular corrosion of stainless steel can be controlled with the application of laser welding.
Vibration Source Contribution Analysis of Plate Structure Using Independent Component Analysis
Kim, Kook-Hyun ;
Journal of Ocean Engineering and Technology, volume 26, issue 4, 2012, Pages 70~76
DOI : 10.5574/KSOE.2012.26.4.070
The independent component analysis (ICA) technique is a source identification method that uses statistical independence to separate source signals from measured signals. It has been successfully applied to various fields such as medical care and communication. In this study, the ICA technique was adopted to analyze the vibration source contribution of plate structures. The theory of the ICA technique is introduced and the procedure of the vibration source contribution analysis based on the ICA technique is proposed. To investigate the applicability of the proposed method to plate structures, numerical examples are presented for a rectangular plate under harmonic force excitations. The results show that the proposed method could become an effective tool for the vibration source contribution analysis of a plate structure.
Investigation of Safety and Design of Mooring Lines for Floating Wave Energy Conversion
Jung, Dong-Ho ; Nam, Bo-Woo ; Shin, Seung-Ho ; Kim, Hyeon-Ju ; Lee, Ho-Saeng ; Moon, Deok-Soo ; Song, Je-Ha ;
Journal of Ocean Engineering and Technology, volume 26, issue 4, 2012, Pages 77~85
DOI : 10.5574/KSOE.2012.26.4.077
A study was performed on the design of a mooring line to maintain the position of a floating WEC (wave energy conversion) system. The procedure to design a mooring line is set up and the safety of the designed mooring system is evaluated using commercial software, Orcaflex. The characteristics curve for one line is analyzed to determine the properties and pretension of a mooring line. While considering the ocean environmental condition and importance of a floating WEC system, a multi-line layout is determined. A 4-point mooring system with 4 lines shows the instability in the yaw motion of the floating WEC system under a designed ocean environmental condition. The redesigned 4-point mooring system with 8 lines is found to be safe on the condition of a harsh ocean environment. The floating WEC system with the redesigned mooring system also shows stable motion in surge and pitch under operating conditions. From a parametric study on the mooring line length, the extreme value of the mooring line tension is found to be very sensitive to the pretension and length of mooring line. The results of this study can contribute to the establishment of a design procedure for mooring lines.
Identification of a Nonproportional Damping Matrix Using the Finite Element Model Updating
Min, Cheon-Hong ; Kim, Hyung-Woo ; Lee, Chang-Ho ; Hong, Sup ; Choi, Jong-Su ; Yeu, Tae-Kyeong ;
Journal of Ocean Engineering and Technology, volume 26, issue 4, 2012, Pages 86~91
DOI : 10.5574/KSOE.2012.26.4.086
A new identification method for a nonproportional damping matrix using the finite element (FE) model updating technique is proposed. Mass and stiffness matrices of the undamped system are identified by FE model updating method. Sensitivity analysis is used to update the FE model, and zero frequencies are considered as design parameters to supplement the information of vibration characteristics. The nonproportional damping matrix is identified through the proposed method. A numerical example is considered to verify the performance of the proposed method. As a result, the damping matrix of the nonproportional system is estimated accurately.